1. Field of the Invention
The present invention relates to a face panel for a color image display apparatus, a panel for a color image display apparatus using the face panel, and a color image display apparatus on which the panel is mounted.
2. Description of the Related Art
It is difficult for a conventional image display apparatus using a Cathode Ray Tube (CRT) called a Braun tube to cope with requirements for an enlargement of a display screen due to its weight, a technical problem for an increase of size of the CRT, and the like. Accordingly, image display apparatuses using a flat panel called Flat Panel Display (FPD) are predominantly used as image display apparatuses at present. Furthermore, liquid crystal displays, a plasma displays, and the like are mainly used as image display apparatuses using FPD.
However, since the liquid crystal display and the plasma display are partially inferior to the conventional image display apparatus using a cathode ray tube (CRT) called a Braun tube in image quality and a response speed, they are required to further improve them.
There is a field emission display (FED) having the same operation principle as that of the CRT to improve the image quality and the response speed of the FPD.
There are characteristics of brightness of a displayed image as important characteristics of a color image display apparatus. The characteristics of the brightness of the displayed image are generally evaluated by luminance and a contrast ratio. The contrast ratio is a luminance ratio of white (maximum luminance) and black (minimum luminance). Since the black luminance is affected by the reflection of external light from an image screen, it is assumed below that the contrast ratio means a contrast ratio in an incident condition that external light incident on the image screen (bright place).
Furthermore, it is assumed that the contrast ratio in the bright place is the contrast ratio which is measured in a condition that external light of 150 lux is irradiated to the image screen at an angle of 45°.
The brightness and the contrast ratio of an image, which is displayed on the image screen and visually recognized by a viewer, depend not only on the level of luminance of the displayed image but also on the surface brightness of the display screen itself. That is, the brightness and the contrast ratio of the displayed image visually recognized by the viewer are determined by the balance between the sum total of the reflected lights when no image is displayed on the image screen, the visually recognized brightness of a fluorescent screen itself, and the like and the luminance of the displayed image which emits light by the fluorescent screen.
Then, the image display quality of a color image display apparatus can be improved by improving the brightness and the contrast ratio of the displayed image.
When the contrast ratio of the FED is improved, it is considered that the technique of the CRT, which has the same operation principle as that of the FED, can be used.
To improve the contrast ratio of the CRT, Japanese Patent Application Laid-Open Nos. 64-7457 and H07-179711 disclose a technique of using a color filter, which has the same color as that of a phosphor, between a substrate and a phosphor layer, the color filter having a function for causing the light emitted from the phosphor to selectively pass therethrough. Japanese Patent Application Laid-Open No. H09-27284 discloses a manufacturing method and like of a color filter of a plasma display. Furthermore, Japanese Patent Application Laid-Open No. 2000-164145 discloses a technique for providing a filter on a surface of a substrate to improve a contrast ratio of a CRT.
Japanese Patent Application Laid-Open No. 64-7457 discloses a color filter which is composed of pigment particles having an average particle diameter of 0.005 μm to 0.07 μm and which has a film thickness of 15 nm to 250 nm.
Furthermore, Japanese Patent Application Laid-Open No. 09-27284 discloses a technique of not only interposing a color filter between a phosphor and the substrate but also forming an external filter to the surface of the substrate (outer surface) opposite to the surface thereof on which the phosphor is formed (inner surface).
Japanese Patent Application Laid-Open No. 09-27284 discloses to form a color filter whose transmittance to a light having a wavelength within the range of the maximum spectrum wavelength of emitted lights ±20 nm is higher than the transmittance to a light having a wavelength of 400 to 650 nm other than the above range in the light emitted from a phosphor layer.
The external surface filter is a filter for supplementing the light absorption of the color filter and has a maximum absorption in a constant wavelength band other than the range of ±20 nm of the maximum spectrum wavelength of the light emitted by a three-color phosphor layer.
Japanese Patent Application Laid-Open No. H07-179711 discloses a pigment-dispersed liquid composition containing an inorganic pigment of 0.5 to 50 parts by weight, at least one kind of a dispersing agent selected from a group composed of sodium salt, ammonium salt or amine salt of acrylic resin, acrylic copolymer resin, polycarboxylic acids, and an aromatic sulfonic acid formalin condensate, and water or a solvent compatible with water. Furthermore, the publication discloses a method of manufacturing a color filter using the pigment-dispersed liquid composition.
Although the contrast ratio can be increased when the transmittance of a substrate to visible light is increased to about 50%, a halation is caused in a portion where a white display is made in contact with a black display. To prevent this phenomenon, Japanese Patent Application Laid-Open No. 2000-164145 discloses a technique for setting the transmittances of a substrate and a filter disposed to an outer surface of the substrate to 60 to 80%, respectively.